(a) Technical Field of the Invention
The present invention relates to piston, and in particular, to a piston mounted within a cylinder.
(b) Description of the Prior Art
Pistons used in conventional small size or portable pump employ TEFLON, a high temperature resistance, wear-resistance material as a material for rings of the pistons TEFLON is an extremely high plasticizing material and the rings are mounted or secured at the outer surface of the piston. The drawbacks of such structure are that, for example, stability of the structure is not sufficient, and air-sealing is poor, which causes non-smooth rotating, air leakage, air compression ratio being insufficient. Additionally, the longevity of the piston is affected.
Currently, another type of conventional piston, as shown in FIG. 1 has a recessed circular slot A2 at the external edge of the piston A1, and the recessed circular slot A2 is mounted with a circular gas ring A3. There is a seal between the ring A3 and the cylinder wall such that high speed reciprocation operation of the piston will achieve the objective of the air compression and air-filling. However, the drawbacks of this conventional structure are that    (1) the binding force between the circular ring and the piston slot is weak and therefore, the circular ring is dislocated or biased;    (2) the tolerance and precision between the circular ring and the piston circular slot has to be accurate. Thus, the inaccurately of the tolerance will affect the stability of the reciprocation process;    (3) if the tolerance is too great motor may be affected and high heat and expansion will occur;    (4) if the tolerance is too small, the air compression is insufficient and air leakage will occur; and    (5) as shown in FIG. 1, if the bearing A4 is dislocated or biased, the air pump will be damaged and the longevity of the pump is affected.